>>23419140I: Actually nothing. There are some things I dislike about Gen I, but there's no individual Pokémon from it I would rather didn't exist.
II: Unown was a terrible idea. Let's make a hilariously useless Pokémon that can only ever learn one move with unreliable type and (pre-Gen VI) power, and make 26 different kinds of it you have to collect! Also it can't breed and all the letters are always found together, so you HAVE to sit around scumming encounters for a stupid amount of time to complete the set!
III: Grumpig. They took an adorable first stage based around a novel concept and evolved it into a boring-ass pig with an ugly color pattern and an equally boring "mediocre special sponge with no distinctive moves" build.
IV: Way too many, but if I have to pick one, it has to be Phione. Not only did they make a legendary Pokémon you can only get from a side game, they made another Pokémon that is literally an inferior clone of it you get by breeding it with Ditto, with no notable traits of its own.
V: Six-way tie between all the goddamn pseudo-starter monkeys that Black and White practically force you to use one of.
VI: Maybe it's just because the selection of new Pokémon is so small, but I can't actually find anything that's aggressively terrible. Some things I somewhat dislike, but nothing I hate.